A tissue microarray is an ordered array of numerous tissue samples, which is attached onto a single glass slide typically 2.5×7.5 cm in size, and also indicates a technology of preparing the above tissue array. Biological tissues useful in the tissue microarray include human tissues, animal tissues and cultured cells. A glass slide onto which a tissue microarray samples are attached is useful for analysis of intracellular proteins, DNA and RNA and microscopic analysis. The slide can be applied for a broad range of in situ assays, for examples, immunohistochemistry, in situ hybridization, special stain and in situ PCR.
In early days of medical and biological fields, biological tissue samples were analyzed at a state of being embedded in paraffin. The paraffin blocks were cut into thin sections (4–8 μm) using a tissue microtome and attached onto a glass slide. However, since the paraffin-embedded tissues in the blocks were bigger than 1×2×0.4 cm in size, only one tissue can be attached onto a single glass slide. Thus, especially when multiple tissue samples are desired to be analyzed, this conventional method is disadvantageous in terms of requiring many slides, many disposable materials and a large quantity of reagents, resulting in high costs for the analyses of the tissue samples, and time consuming. The disadvantages of the conventional method further may be lack of consistency and reliability since the tissue samples compared with each other, are analyzed separately by individual.
To overcome these problems, International Patent Application No. PCT/DE00/04647 discloses a method of preparing a recipient block capable of receiving multiple tissue samples. In detail, the method of preparing a recipient block comprises punching holes to the bottom of a tray-type aluminum block and striking a cylindrical pin into each hole. This provides a template for the recipient block; pouring a molten, high temperature paraffin solution into the template; and cooling the template to provide a plurality of cylindrical openings. The International Patent Application also discloses a method of preparing a tissue microarray block receiving multiple tissue samples, comprising arraying multiple tissue samples into the cylindrical openings provided in the recipient block, pouring paraffin onto the recipient block and cooling the recipient block
Korean Utility Model Application No. 20-1999-0025914 discloses an apparatus for preparation of a tissue microarray, which comprises a plurality of tissue storing units including a storing cassette to insert a plurality of tissue samples thereinto and to be then filled with paraffin an outer surface thereof; a puncher to punch off the solidified tissue samples at a state of being integrated with the paraffin into a single structure in the storing cassette to provide tissue blocks with a constant diameter; and a block storing unit including a plurality of tissue inserting holes to insert a plurality of the tissue blocks thereinto at a state of being integrated therewith into a single structure.
However, the conventional methods disclosed in the International Patent Application and the Korean Utility Model Application have a significant problem since the above tissue microarrays are prepared using paraffin-embedded tissue blocks. Typically, the paraffin embedding method of tissue samples arrayed in a recipient block includes heating process. During the heating process, paraffin is melted, and this melting of paraffin leads an array of tissue samples to fall into disorder or the tissue samples to be mingled with each other. This problem can be overcome by carrying out the paraffin embedding at low temperatures. However, several hours (5–12 hrs) are required to accomplish paraffin embedding of tissue samples at low temperatures. In this case, tissue samples are often not fused with paraffin, causing separation of the tissue samples from the paraffin block upon sectioning of the resulting tissue microarray. In addition, there is another problem with the conventional parafin-based methods, as follows. Since parafin is opaque white in a solid phase, there is a difficulty in determining states and positions of tissue samples when the tissue samples are arrayed in a recipient block being embedded in paraffin.